I've had / have several from both. Some considerations would be the rifle that you're attaching it to first and foremost. If you have a heavier rifle and require a fair bit of height, something like an AccuTac SR5 is going to provide more stability than say an Atlas PSR. The Atlas legs generally have a little bend to them when extended, and the AccuTacs are generally stiff.
If you're only considering these two and you're planning to do BR - the FC-G2 is a fine choice. My only gripe with it is the leg height. It does not extend as high as I would like it to, so if you're shooting off a mat or on the ground from a position that requires max height, it'll come up short. For this reason, I have swapped legs with my SR5-G2 a couple of times.
Weight is another factor. The AccuTacs are fairly heavy compared to the Atlas's.
The tilt adjustment on the AccuTacs trumps the tilt on every Atlas that I have owned. It's easy to manipulate and somewhat of a pleasure to operate.
Noise - the AccuTacs are louder to operate than the Atlas's. When hunting, you will develop a sound dampening technique with your fingers after a while to extend the AccuTac legs. The caveat is that the leg mechanism will "bite" you sooner or later (I've had a few blood blisters of my own). The Atlas's legs can be a pain to work, but you get used to them.
QD's are great on both; a non-issue IMO.
At the end of the day, the keepers from just these two for me are:
- FC-G2
- SR5-G2
- BT47-LW17 (exclusive to my Lelya and Leshiy)